Design Of High Performance CMOS VCO

The explosive growth in wireless communications has driven people to research and produce wireless transceivers at low-cost, low-power and smaller size. Recently, all of the RF components, such as low-noise amplifier(LNA), mixer, voltage-controlled-osciIIator(VCO), and IF Filters, seem possible to be integrated by the development of CMOS technology. Voltage-control-oscillator is the crucial components of wireless transceivers, it provides local signal and clock for the whole circuit, its performance parameter, such as: phase noise, tuning range, power consumption, have great effect on wireless transceivers, So how to design a high performance Voltage-controlled-oscillator is a real challenge.In this thesis, the theory and practice of LC VCO are researched, and several key techniques were discussed in simple way.Firstly, two oscillator theorems: negative-feedback theorem and negative -resistance theorem, are presented and the conditions of startup, equilibrium, stabilization required for oscillator are discussed respectively. Several classic oscillator circuits such as: Colpitts and Hartley are introduced.Secondly, we introduce two types of VCO: ring VCO and LC VCO, and made a comparison between them, it is obvious that LC VCO are suit for FR application. The physical model for MOS varactor and planar spiral inductor are present, which improve our understanding of these two devices' key function to VCO.Phase noise is the most important criterion in the VCO performance, we pointed out that phase noise comes from thermal noise, flicker noise, supply and substrate noise, and each of them we had a brief introduction. We have studied two analysis methods of phase noise: linear time invariant and nonlinear time invariant. The characteristic of different area's phase noise can be successfully explained by these two methods. We also summarized severaltechniques to reduce phase noise: increase the value of Q; improve output waveform; use the device with low flicker noise.In the foully part, some details about library and EDA tools are discussed,all the device in this design are from 0.18 RF library in TSMC, schematic edittool is virtuoso, simulator is spectre, both of them are from Cadence. Secondly,we introduced how to choose varactor and inductor which are crucial to VCO. Transconductance and swing are important to phase noise, in order to optimize the design, we had great efforts on discussing them. Finally, we found a best way to tradeoff different variables in the design. Emitter follower was adopted to satisfy the requirement of driving capability.At last, results about this design were brought out. It can be seen that output waveform of this is more symmetrical than single-couple PMOS structure VCO. This work satisfies other spec of 802.11b protocol applications too. To use PFN (power frequency normalized) method, we can make a comparison between this work and reference works. It is obvious that this work has a better performance.